How to generate non-repeatable random number in simulink in same session

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Ian Van Giesen 2020-6-24

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https://ww2.mathworks.cn/matlabcentral/answers/554098-how-to-generate-non-repeatable-random-number-in-simulink-in-same-session

编辑： Ian Van Giesen 2020-6-25

I'm trying to use poissrnd to get a random distribution of numbers for determing water usage from a washer using a user defined function block in simulink. With lambda = 0.052, I get the same 'random' numbers everytime time I run the simulation. I tried using rng('shuffle') in the function block, which works but causes run-time to shoot dramatically up. I also tried simply typing rng('shuffle') into the initfunction and startfunction for the model setting, but that didn't work at all, ie same results over again.

Did some reading around of questions posted about this topic, and the closes I could find is here. How to achieve non-repeatable randomization in Stateflow? But I'm lost as to how to create the mat file, and where to save it, and how to work with the init function to call (?) the mat file to generate a random seed for each simulation run in the same session.

Can anyone provide any guidance? Thank you.

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Answer 1

Fangjun Jiang 2020-6-24

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https://ww2.mathworks.cn/matlabcentral/answers/554098-how-to-generate-non-repeatable-random-number-in-simulink-in-same-session#answer_456592

The MATLAB Function block is executed at every simulation step. For this case, I would suggest using rng() and poissrnd(0.52,N,1) to generate data offline and then import it into Simulink using "From Workspace" block.

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Ian Van Giesen 2020-6-24

编辑：Ian Van Giesen 2020-6-24

Okay, great thank you for the response, but I wasn't able to figure it out I think. Just in case I did something wrong or in case other people after me see this response, this is what I did to set the stop time and step size parameters in the simulations. I went to model settings and under the 'Solver' category, I changed the Stop time variable to tStop and the changed the type of solver selection to Fixed-step and inserted tStep as the variable for the Fixed-step size (fundamental sample time) variable.

I created a .m file with the preset initial condition I ran for this simulation.

However, when I ran the simulation, everything seemed to go okay, except when I tried to open a scope attached to the [time, data] block. I was told that it had '1001 signals' and 'may take several minutes or hours to visualize'. I wasn't able to get a picture of that, because simulink froze.

Any guidance?

Edit: I was able to open up part of the scope view, but it didn't tell me much.